Discussion Topic

The way the thermostat in engineered in a suby EJ engine wont allow the neck to seal without the tstat in place, its a circumferential rubber gasket around the tstat itself. Its $30 for an OEM part even from the dealer, plus a gallon of coolant. Besides, when you drain the coolant, you have to run the engine when you fill it to get all the air bubbles out, filling it bit by bit as you go to replace the displaced air.

Check your oil, does it still look like oil? does your coolant still look like coolant, or does it have traces of oil on the surface? If your oil looks like brown snot or if youve some some signs of oil in your coolant, the headgasket it suspect, if not, youre probably fine.

Get under there and change the tstat and replace the coolant. Coolant gets old and wears out, loses its properties. Bleed all the air out get it full of coolant, run your heater while you do so, until your cooling fans come on. Drive it normally to see if it fixed the issue.

The old EJ25 DOHC 97-98 will take a headgasket fine. I had one that was repaired early on that was just fine. A friend had one also that was repaired and its was fine for many years, still is. Totally worth the repair if the rest of the car is intact.....but change that thermostat, you could have been done by now.

Most likely is that your thermostat is stuck shut and needs replacing, thats all. If you havent replaced your coolant in 30k miles, then that needs it too.

Subarus have a funny rep. Some of them run with no problems. Even some of the ones with known issues. Others just seem to be cranky.

I would totally check the thermostat first if no other signs are showing up. Especially on a low milage vehicle.

I know a guy that was given an old subbie with high milage.. The owner thought it was toast because of an overheating issue, so just gave it away. The guy he gave it to put a 10 dollar can of stop leak in it and drove it for 4 more years.

Here in the mountains there are lots of people who drive cars until they are dead dead. Not just.. I think its dead. I followed one guy out of the park whose car was on fire. It leaked oil so bad it would catch on fire. I blinked my lights at him and honked my horn and got him to pull over. He got out with a fire extinguisher and sprayed it, then said.. yeah.. it does that. Then got back in his car and kept going. I just shook my head.

I drove on old mazda GLC for 3 years that I paid 50 dollars for. I put new tires on it for 120 dollars and that was it. When it finally died, I sold it to a guy for 50 dollars for a parts car.

Honestly, fix the damn thermostat. You will have a solid car again. Sorry to sound like a dick, but all this silly speculation is wrong. As a former mechanic who has done all his own work for 20 years, on my sixth subaru and having just replaced my own thermostat on my 2006 WRX with 155k miles on it, just swap the thermostat and fill it with fresh coolant. Based on your description, the head gasket is not the culprit.

It's true replacing the thermostat is easy, that's probably the thing to try first, even if it's likely not the problem.

The gaskets in the 96-01 Subies had problems long before blowing out completely, they leaked gas intermittently into the cooling system. The gas pushes the coolant out, the engine gets hotter pusing more gas through, and bingo, it overheats. Hence the 'sporadically'.

When the gaskets in mine were blown completely, it was obvious. The car didn't run properly.

But the damn thing overheated sporadically, as you say, for a long time before it overheated so bad that it blew the gaskets and (I think) warped the heads.

It overheated sporadically despite replacing the thermostat, water pump, and radiator.

YMMV

My problems started at ~90K miles

In fact the only thing that fixed that car was putting a whole new engine in it, which my buddy did at a cost to him of ~$1K plus a lot of his own labor. Now it's a good car.

Hot damn, leave town for a day and come back to all of this useful input. Thanks one and all.

The odd thing about the overheating in this car: Before driving it, I made sure that the coolant was right at the full line in the recovery bottle and where it needed to be under the radiator cap.

So when it overheated the last two or three times, I've pulled over and let idle until the temp came down, then turned her off.

Invariably, within 10 to 15 minutes there is not coolant left - empty recovery bottle, none under the cap in the neck. If I pop the hood right after overheat, I can see and hear it boiling in the recovery bottle, and this boil causes a fair amount of it to bubble out of the air hole at the top of the recovery bottle and drip to the ground. A puddle of it accumulates there on the ground under the bottle, but it just doesn't seem like the total volume of the coolant. So where in the hell did the rest of the coolant go? Compression is perfect, according to the mechanic. So no clue.

I'll check back in after replacing the thermostat. At this point our expectations are very very low for this car. If we do end up letting it go for scrap, I'll give pref to anyone who has expressed interest.

Wanderlust, if the thing does get running consider yourself in God's pocket this summer. You can sleep like a king in the back of that pos.

For my money, this right here from the link in my OP is what I've got on my hands:

When the gaskets are starting to fail, some of the combustion gasses (exhaust usually) are forced past the thin metal head gasket into the cooling system. Little by little these gasses accumulate in the cooling system and begin to create an “air pocket” if you will, inside of the engine cooling system. Depending on where this air pocket circulates to, or how large it is, it can create numerous issues. If it becomes trapped around the water pump or thermostat it can prevent coolant from flowing through the engine, which results in almost immediate overheating.

But! The local Suby mechanic used a gas analyzer at the recovery bottle's mouth to sniff for hydrocarbons and found 0 ppm. He also did a compression check and found the system to be airtight. He also commuted in my pos car for a week from dt Oakland to Walnut Creek and had no issues. All good signs. So I'll try the damn thermostat.